The motor vehicle industry is continuously manufacturing and developing sealing elements and sections having low friction and abrasion resistance properties. These elements and sections can be extruded from certain polymeric materials. One example of an extruded abrasion-resistant section is a static seal. Static seals, such as weatherstrips, are mounted on an automobile window to provide a seal between the glass and the automobile body to prevent wind noise, water leaks, and particulate matter from entering the automobile. Another example of an extruded abrasion-resistant seal is a dynamic seal. Dynamic seals, such as weatherstrips, are typically employed to seal parts that are capable of motion relative to one another. According to further examples of these seals, foaming agents can be employed to generate porosity in the seals to offer further weight savings.
Weatherstrip formulations that make contact with various sections of automotive glass doors, and/or other sections of an automotive body traditionally utilize thermoplastic vulcanizates (TPV), styrene-ethylene/butylene-styrene copolymer (SEBS), or ethylene propylene diene monomer (EPDM) rubber to achieve desired sealing performance. Monolithic TPV, SEBS and EPDM materials typically exhibit densities in the range of 0.75 g/cm3 to 1.3 g/cm3, depending on whether foaming agents are employed. While monolithic TPV-, SEBS- and EPDM-based seals offer certain property and density ranges that can suitable for particular sealing applications, various portions of the seals may require differing properties and/or densities relative to other portions of the same seal. Further, TPVs are relatively easy to process, but sealing performance can be limited in terms of resilience or sealing ability over time and material costs tend to be high. Similarly, EPDM rubber formulations often require many ingredients (e.g., carbon black, petroleum-based oil, zinc oxide, miscellaneous fillers such as calcium carbonate or talc, processing aids, curatives, blowing agents, and many other materials to meet performance requirements), which tend to increase their material cost.
EPDM-based seals are also costly from a process stand point. The EPDM constituent ingredients are typically mixed together in a one- or two-step process prior to shipping to an extrusion facility. At the extrusion facility, the ingredients and rubber compound(s) are extruded together to form a final material, which is subsequently formed into automotive glass contacting weatherstrips. Hence, the extrusion process used to manufacture weatherstrips can include many stages, depending on the type of EPDM or other types of resins, and may additionally require long lengths of curing ovens. For example, extrusion lines of up to 80 yards in length that are powered by natural gas and/or electricity may be required. Much of the natural gas and/or electricity is used to fuel hot air ovens, microwaves, infrared ovens, or other types of equipment used to vulcanize the EPDM rubber compounds. The vulcanization process also produces fumes that must be vented and monitored to comply with environmental requirements. Overall, the processes used to fabricate these traditional EPDM-based seals can be very time consuming, costly, and environmentally unfriendly.
Mindful of the drawbacks associated with current TPV-, SEBS- and EPDM-based sealing technologies, the automotive industry has a need for the development of new compositions and methods for manufacturing seals, such as weatherstrips, that are simpler, lighter in weight, lower in cost, have superior long-term load loss (LLS) (i.e., ability to seal the glass and window for a long term), offer variable properties within a given part, and are more environmentally friendly.